Twin Scroll
 

I am looking for some confirmation that the exhaust housing on an H1C is a twin scroll design. Working on my header design, want to make sure it's a twin scroll so I can nail down the design (cylinders 1, 2 and 3 isolated to one scroll, 4, 5, and 6 to the other). If I can optimize and equalize the pulsing my turbo will spool much faster, have better transient response, and have better top end flow to boot. I can't live with the stock exhaust manifold much longer.... [duhhh]

Twin scroll as in divided housing? Yes.

I think they all are sans the HY35W and the HE351CW (maybe VGT too)

On larger industrial diesels, I was always taught that separated exhaust manifolds ("pulse" style turbocharging) resulted in superior spool up and frequent load change (most our generators had split exhaust manifolds)

"Constant pressure" style turbos were best for being more efficient in a constant high load/pressure situation. Most our Main's had a constant pressure style set up.

With that all said, our high speed Cummins are hard to compare to 720-900 rpm Wartsilas, Mans, and Cats and especially a 90 rpm Sulzer or Man B&W.

:eek: Is that how it looks under my hood while going down the road ??

I think I better move some of the wires and plastic stuff somewhere else.





I didn't know there was a difference until reading these previous postings.

That explains why there are divided plenum turbo gaskets and also those that are just one open rectangle.

I once had my turbo off for some reason or other and the old gasket --- a divided one --- was torn; a friend had a pack of a dozen or so that were open rectangles with no divider and gave me a couple.

I ran with that for a couple years and never knew the difference. :cowboy:

i've done the same thing as you bearkiller, except i misplaced the divided gasket... i didn't notice a difference either.

The difference would only come into play if the exhaust was a split manifold, as in 1,2,3 isolated to one scroll, and 4,5,6 isolated to the other scroll.

I just took a 18.5 exhaust off a 93.

YES it is a two port type design (123)(456) you can even see the divider casting going around the exterior of the housing.

Isn't the stock manifold split?

So since this thread is a few months old you got and pictures/drawings of your new header?

It sure is. That's why when we drill and tap for EGT probes, it's in the back half of the flange which reads cylinder 4, 5 and 6. I've heard a lot of stories of others finding out the hard way that the manifold is split [laugh].

Thats a crazy pic!:o I would'nt want mine doing that.

ive had that picture on the wall of my garage for about 5 years now.

Kind of related. I cut the divider out of a 12cm. Hurt spool and cruising egts. Waste of time.

https://www.dieseltruckresource.com/...usings_002.jpg

The hy35 he341, and He351CW have an undividing housing. Im trying to remember on the vgt but if I remember right it is undivided as well. The h1cs and hx35s have a split or twin scroll housing as do a lot of bigger or aftermarket turbos.

I've always wondered why they divided them or why they were undivided other than the wastegate being able to relieve all cylinders instead of 3 unless you drill the hole through the divider. Is it just for spoolup reasons? Cuz the Hy35 and He351 and 341 spool faster than any stock cummins turbo with an undivided housing although they do have the 9cm exhaust housing which is the smallest.

I know some people port their housings and say to do it but wouldn't it hurt spoolup?

Volvo did away with the pulse style manifolds on the Volvo and Mack motors a few years ago during one of the emissions change-overs.